1. Field of the Invention
This invention relates to the fabrication of thick film resistors for use in hybrid microcircuits and more particularly, to a method of forming dielectric material on a substrate material during the fabrication of the thick film resistors and subsequent removal of the thick film resistors from the carrier substrate.
2. Description of the Related Art
Various techniques for the fabrication of thick film resistors have been proposed in the past. Thick film resistors have been in use in the electronics industry for more than the past 20 years. One typical application has been to use the thick film resistor in conjunction with a conductor network in a hybrid circuit. Recently, many users of such device have directed development activities toward the making and use of pick-and-place technology to fabricate the hybridized circuitry. The resistors currently being evaluated for most of these applications are typically cermet chip resistors. These resistors are in effect separate thick circuits consisting of one resistor terminated with a conductor. The structure of these resistors is like that illustrated in FIG. 2 of the prior art, and consists of an alumina substrate 23 on which is located a resistor coating 20, a first conductor such as 22 located in contact with the resistive material 20 and second edge mounted conductor 24 connected thereto and the resistive material 20 and first conductor 22 is covered by glass encapsulant 21. A comparison of this type of resistor to that of a typical thick film resistor, which consists of an alumina substrate 13 on which are formed conductors, such as conductor 12 in contact with resistive material 10 and with a glass encapsulant material 11 superimposed over the resistive material, as shown in FIG. 1, will show only the addition of the edge conductor 24. The prior art techniques exhibit a number of drawbacks, including high cost, the fabrication, difficulty in mounting and establishing appropriate electrical connections to the unit. Many of the techniques proposed require inefficient manual soldering operations for a connection, while others, in an attempt to accommodate dip soldering or reflow soldering techniques, use such uneconomical techniques as vacuum, electron beam evaporation or sputtering to achieve devices where a connection can be made by dip soldering or reflow soldering.
In yet another instance, films may be deposited by printing metal glaze paste or by similar means and then the films are fired to form lateral electrodes. The high temperature of the firing operation called for thus causes deterioration of the low resistance temperature coefficient of the resistor and the high stability of the resistives which characterize the resistor.